Flashcards
Physics Flash Cards
Flashcards do conjunto (70)
- 1Give the order of the Electromagnetic SpectrumGamma Rays, X-rays, Ultra Violet, Visible light, Infrared, Microwaves, Radio Waves
- 2In what four types of energy transfer is energy transferred by particles?Condensation
Convection
Conduction
Evaporation - 3Some characteristics of IR:-Heat
_All objects
-Hotter objects-move
-Electromagnetic Wave
-Different coloured surfaces absorb and emit differently
-Can detect with your skin, but not your eyes.
-Can detect with a special camera (thermogram)
-No particles required - 4Properties of StatesSolid- Particles are very close and vibrate around fixed positions. Solid has fixed shape and volume.
Liquid- Particles are close and move around. Liquid has fixed volume, and fits the shape of the container.
Gas-Particles are very far apart and move around randomly and very quickly. Gas fills space available, and has no fixed volume and can spread out. - 5Explain conduction in a metal (and graphite)One end of a metal bar is heated. The atoms near the heat gain energy, so they vibrate more vigorously. They collide with other atoms, passing on energy, and so forth. Free (delocalised) electrons also gain energy, so vibrate and move along the length of the metal, colliding with atoms, helping them to vibrate.
- 6Why are metals such good conductors of energy?1) Atoms arranged neatly in rows, so can bump into each other.
2) Presence of free electrons. - 7Explain the process of convection (Gases and Liquids)Particles in the heated end of the fluid gain energy, so move around much more, taking more space. Liquid expands, and becomes less dense. The liquid becomes lighter than the surrounding liquid, so rises. As it rises, it meets cooler liquid at the top, so therefore the liquid cools. The particles lose energy, move around less, and the liquid contracts and becomes more dense. The liquid falls. This movement is called a convection current.
- 8Convection in a radiatorParticles in the air near a radiator gain energy, so the gas expands and rises. Warm air meets cooler air, so becomes more dense and falls. Throughout the cycle, the room gets warmer and warmer.
- 9Factors affecting heat loss1) Shape of an object
2) Surface area : volume ratio (higher-more loss) of object
3) Material the object is sitting on
4) - 10How cooling fins aid heat lossThey increase the surface area, so more heat is radiated away from lots of different surfaces.
Used on backs of fridges, car radiators, microchips, motorbike engines. - 11What is a U-Value?The energy per second that passes through 1 square metre of material when the temperature difference across it is 1 degrees.
High U-Value-lot of energy transferred
Low U-value-little energy transferred - 12Payback time=?Payback Time=
Cost of Insulation
____________
Savings per year. - 13What is Specific Heat Capacity? (Give Units)Specific Heat Capacity (J/KgC)=
Energy (J)
------------
Mass (kg) X Temp change (C) - 14Equation for Energy Transferred? (Give Units)Energy Transferred (kWH)=
Power (kW) X Time (hours) - 15Explain how steam is used to turn a turbine?Water is evaporated in a boiler using coal/oil/natural gas/biofuel. The steam is channelled towards the turbine, which turns, and turns the generator, generating electricity. The steam is then channelled through a condenser, and condensed back into water. It is taken back to the boiler, and the cycle repeats.
- 16Explain how nuclear fuel is used to generate electricity? Refer to nuclear fission.The two types of nuclear fuel are plutonium and uranium. They generate heat through a process called nuclear fission.
In this process, the nucleus of the atoms of plutonium and uranium are split into 2 smaller nuclei. This process releases a lot of energy. This energy is used to make steam to turn a turbine. - 17Give some advantages and disadvantages of Nuclear Fuel?Adv:
1) Lots of electricity from a small space ( 10,000kg of fossil fuel gives same energy as 1kg of nuclear fuel)
2) Doesn't produce any polluting gases.
Disadv:
1) Radioactive waste-can kill/cause cancer.
2) Waste is difficult to dispose of.
3) Expensive to decommission (shut down and dismantle). - 18Give some advantages and disadvantages of Fossil Fuels?Adv:
1) Lots of energy from small space.
2) Gas power stations are quick to switch on and off.
3) Gas tail flow-easy to transport.
Disadv:
1) Non-renewable
2) CO2 produced
3) Sulfur oxides produced-cause acid rain. - 19Give some advantages and disadvantages of wind power?Adv:
1) Lots of energy
2) Easy to collect energy-even weak winds can turn the turbines.
Disadv:
1)Loud and "ugly"
2) Won't collect much energy on windless days.
3) Have to transport electricity - 20Give some advantages and disadvantages of tidal power?Adv:
1) Tides are constant
Disadv:
1) Expensive
2) Affects environment. - 21Give some advantages and disadvantages of hydroelectric power?Adv:
1) Utilises rainwater
Disadv:
1) Floods habitats
2) Can only be set up in specific locations
3) Expensive - 22Give some advantages and disadvantages of wave power?Adv:
1) Renewable
Disadv:
1) Need to withstand storms
2) Not a constant supply of electricity
3) Lots of cables and buildings are needed along the coast to connect the wave generators to the electricity grid
4) Affects habitats of marine life and birds - 23Give some advantages and disadvantages of solar power?Adv:
1) Useful where small amounts of energy are needed, or in remote places (eg. islands)
2) Cost nothing to run
Disadv:
1) Very expensive to buy
2) We need lots of panels, and plenty of sunshine, to generate enough energy to be useful
3) Converts less than 10% of solar energy they absorb into electrical energy. - 24Give some advantages and disadvantages of geothermal power?Adv:
-Constantly produced
Disadv:
-Limited places to set up stations; volcanic - 25What is pumped storage?-Hydroelectric power station
-Water flows down turning a generator
-Can be started very quickly
-When there is little demand for energy, water from the lowest reservoir can be pumped back up to the top, where the water is stored. When the demand rises, the water flows back down.
-This is good because, when there is an unexpected surge of electricity requirement, the system can respond quickly. - 26THE NATIONAL GRID- Path of electricity-Start at power station
-Step-up transformer
-Pylons-carry electricity around country
-Step-down transformers
-Customers (buildings, homes etc.) - 27Why are step-up transformers and step-down transformers used?Electricity leaves power station at about 11,000V
Step-up:
-Increase the voltage to about 132,000V
-Decreases current (rate of electricity flow) to reduce heat, so less energy is wasted to the surroundings
Step-down:
-Decrease voltage back down to 11,000V, then down to 240V so it is safe to use. - 28Pros and Cons of underground electricity cables?Pros:
-Cables are hidden
Cons:
-Expensive to lay cables (digging required)
-Expensive to repair
-Need added measures i.e. waterproofed
-Special casing to prevent heat - 29Problems with overhead electricity cables?-Spoil landscape
-Health issues (electromagnetic field) - 30In the National grid, why do we need a high voltage?-As current through a wire increases, the wire heats up
-We want to waste as little energy as possible
-Power=Current X Voltage
-If we double the voltage, we can halve the current and maintain the power
-We transmit electricity at high voltages. - 31How do waves transfer energy?By vibrations
- 32Two types of waves?Transverse
Longitudinal - 33Examples of transverse waves?-Rope
-Water
-Radio waves
-Light waves - 34Examples of longitudinal waves?-Sound
-SOME seismic waves (earthquakes) - 35What is meant by mechanical waves? Examples?Mechanical waves need a substance or material to travel through (a medium)
e.g. rope, water, sound, seismic - 36What name is given to waves that do not require a medium to travel through?Electromagnetic
Can travel through a vacuum - 37Parts of a transverse wave?-Wavelength (the distance from one peak/crest, or trough, to the next)
-Amplitude (the distance from the middle part of a wave to the peak, or to the trough (height of a wave)) - 38Parts of a longitudinal wave?Rarefaction ("stretched bit")
Compression ("squashed bit") - 39How are transverse waves produced?Up and down motion
-The direction of vibrations is at right angles to the direction of the wave energy.
-Travel right to left - 40How are longitudinal waves produced?Side to side vibrations
-Oscillation is parallel to the direction of the waves - 41Speed of light?300,000,000 m/s
- 42Equation for wave speed (give units)Wave speed (m/s) =
Frequency (Hz) X Wavelength (m)
Wavelength=Distance from one trough, or crest, to the next
Frequency=Number of waves that pass a certain point, Hertz
1 Hz=1 vibration per second - 43Word for wave speed?Velocity
- 44What is diffraction?-Spreading out of waves under certain conditions.
-For example, if water waves hit a barrier, they pass through the gap in a barrier, so the waves spread out. - 45The rate of diffraction depends on?The size of the gap in a barrier
- 46What is the effect of diffraction?When a lot of diffraction occurs, the sound spreads out through the area (e.g. room).
- 47Rule of reflection angles?Angle of incidence=
Angle of reflection
i=r - 48What is refraction? Give a detailed example-When waves change direction.
e.g. :
-Take a glass prism and shine a ray of light through it. The light travels from one medium to another (air to glass), then again (glass to air). When the light hits the glass, it bends towards the normal (an imaginary line at right angles to the surface (glass))
-When the light hits the air at the other side of the glass, it bends away from the normal. - 49Refraction in water?-When waves change from deep to shallow water, they bend towards the normal.
-If waves move in line with (parallel to) the normal, there is NO change in direction. - 50Light to water (refraction)? Effect?-When light rays travel from water to air, they bend away from the normal.
-Therefore, a person watching sees an object in the water at a different position. - 51How are light rays (waves) reflected?-A light ray is shone onto a reflective surface (e.g. a mirror).
-The light ray is reflected at a right angle from the surface at the normal.
-The angle of incidence is measured from the normal, as is the angle of reflection - 52What is a virtual image?An image formed where light rays appear to come from
Virtual images are not real
They look like they are coming from the back of the mirror.
They are upright
They are laterally inverted (left in real life=right in the image) - 53Where is a virtual image formed?Where the lines of incidence and reflection meet behind the mirror
- 54What causes sound?Vibrations
- 55What machine is used to convert a longitudinal wave (produced by an object making a sound) into a transverse wave? (Shows sounds)?Oscilloscope
- 561)Frequency=? 2)Amplitude=?1)Pitch
High frequency=high pitch
2)Volume
High amplitude=loud - 57What is an echo?A reflection of sound
- 58How is an echo produced?A noise is made. Sound waves travel through the air as longitudinal waves, then hit an obstacle and returns to the source (is reflected).
e.g. a ship bounces sounds of the bottom of the ocean to measure distance (echo location)
Bats use echoes to navigate - 59What is the Doppler Effect? (sound)When an object passes you, its sound waves become squashed because object is moving (wavelength decreases +frequency increases)
This makes the pitch higher as the object passes you
As the object goes past, wavelength increases and frequency decreases. Pitch is lower. - 60Explain redshift?-Visible light region of EM spectrum
-Range of colours-only there because wave frequency changes
-Long waves = red
-Short waves = blue
-Objects in space moving away from us have stretched light waves (red-redshift)
-Objects in space moving towards us have squashed waves (blue-blueshift) - 61Distant galaxies look red/orange in colour because...they are rapidly moving away from us
- 62Which are moving quicker?- Galaxies furthest away from us, or galaxies closest to us?Furthest away
- 63What is the Big Bang Theory?Once there was a single point in space, called singularity, where there was a massive explosion that created everything in the universe. Now, the universe is rapidly expanding in all directions.
- 64What is CMBR?Cosmic Microwave Background Radiation
Microwave radiation that was present at the Big Bang, and has spread out in space.
-Was found in 1965 by accident
-Evidences Big Bang Theory - 65Uses of Radio Waves?-Radio
-TV
-Bluetooth headsets
-Mobile phones - 66Uses of microwaves?-Mobile phones
-Satellite TV - 67Uses of IR-TV remote
-Fibre optic cables (connect internet) - 68Uses of light?-Cameras
-Fibre optic cables - 69Uses of waves (varying wavelength)?-Microwaves = satellite TV and phones because microwaves can travel between satellites in space and the ground. Also, they spread out less so the signal doesn't weaken as much
-Radio waves <1m=TV broadcasting from TV masts because they can carry more info than longer waves
-Radio waves 1m-100m= Local radio stations and emergency services because range is limited to area around transmitter
-Radio waves>100m=national and international radio stations because they have much longer range than shorter waves - 70The shorter the wavelength of radio waves...-The more info they carry
-The shorter their range (increasing absorption by atmsphr
-The less they spread out (diffract less)
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- FlashCards sobre Physics Flash Cards, criado por George Murray em 12-05-2015.
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